1. Field of the Invention
This invention relates to connectors provided with means for reducing cross-talk, to enable high speed data transmission.
2. Summary of the Prior Art
There is an increase in demand for cable and connection systems to transmit digital signals at high speeds. As frequency increases, emission of "noise" increases, and this is a particular problem for closely positioned conductors which are subject to what is called cross-talk. Beyond a certain transmission frequency, cross-talk becomes unacceptably intense and thus limits the speed of data transmission. In cables, one of the ways of reducing cross-talk is by twisting pairs of conductors, where one conductor of the pair is for transmitting a positive signal, and the other conductor for transmitting a negative signal of equal intensity and timing as the positive signal. This is called a differential pair due to the nature of the opposed signals in the pair. Due to the twisting about each other, magnetic and electrical fields emitted from each of the cables cancel each other out and thus noise emitted from the pair is very low. Such pairs can thus be placed within a cable and positioned closely together whilst nevertheless transmit high speed electrical signals.
One of the problems however occurs at the connection end, where the conductors are connected to terminals within the connector. Terminals of connectors are often positioned in juxtaposed parallel relationships, and exhibit more cross-talk than between conductors of the cable. One way of reducing cross-talk effects is shown in European Patent Publication No. 583 111 where conductor pairs of a connector are crossed-over, thus behaving in a similar manner to that of a twisted cable. Crossing-over of contacts in connectors is also shown in U.S. Pat. No. 5,186,647. The latter shows cross-talk reduction in a modular jack, which is a standardized connector widely used in telecommunications and computer data interconnection systems. Standardized modular jacks and corresponding plugs for connection thereto, were initially designed and used for low speed data transmission systems, and are thus not necessarily the most effective connection systems for use with high speed data transmission. Due to their widespread use however, there is a need to improve the data transmission speed capabilities of modular plug and jack connectors whilst respecting the standardized interface requirements.
Another means of reducing cross-talk is by judicious capacitive or inductive coupling between conductors of the connector as shown in U.S. Pat. No. 5,326,284. In the latter, the connector (modular jack) is positioned on a printed circuit board (PCB) having circuit traces thereon that are arranged in such a manner to couple the conductors by means of inductances and capacitances. The purpose of the coupling is to neutralize cross-talk present in the line by further coupling of the conductors to an opposite signal of equal intensity (a differential signal). Furthermore, the capacitances and inductances can be adjusted to match the impedance of the connector with that of the cable to reduce reflection of signals. Provision of a PCB however requires an extra component and increases the cost of the connector assembly. Furthermore, the volume of the connector is also increased. The latter also means that some connectors cannot be provided with a PCB, for example provision of a PCB in a modular plug would not be feasible.
G.B.-A-2 271 678 shows a modular jack with terminal contacts having a mating portion, an IDC wire connection portion, and capacitance portions extending integrally via linking portions therebetween. The capacitance portions are laterally offset from their mating portions and are positioned over the capacitance plates or the other contacts, for the purpose of reducing crosstalk between conductor pairs.
U.S. Pat. No. 5,226,835 shows a four conductor patch plug having terminals with a contact portion and an IDC wire connection portion, adjacent terminals being crossed over at a mid-portion between contact and connection portions thereby adding a controlled half-twist to conductor pairs to reduce crosstalk.
It would be desirable to have an interconnection system that is not only cost-effective, but also compact and that is for high speed data transmission, the connector thus having reduced cross-talk and controlled impedance. It would also be desirable to provide the latter aspects in a standardized modular plug connector.
It is an object of this invention to provide a compact and cost-effective connector for high speed signal transmission.
It is an object of this invention to provide a standardized modular plug capable of high speed data transmission.
It is a further object of this invention to provide a compact and cost-effective means for reducing cross-talk in a connector for differential signal transmission, and that can be impedance matched with a cable connection thereto.
Objects of this invention have been achieved by providing a connector comprising an insulative housing and a plurality of juxtaposed contacts mounted thereon, the contacts having a wire connection portion and a mating portion for contact with terminals of a complementary connector, the contacts further comprising plate portions for capacitive coupling between contacts. In an advantageous embodiment, the contacts are stamped and formed from sheet metal, and are mounted in a standardized modular plug connector. Some of the contacts of the connector may comprise thin extensions between the contact portions and plate portions, whereby the thin extensions allow a cross-over in the position of the plate portion with respect to the contact portion such that the corresponding contact can be capacitively coupled to another contact beyond the adjacent contact. The mating portion and connection portions of the contact could be substantially planar, whereby the connection portion comprises insulation piercing contacts for connection by means of piercing to conducting strands of insulated conducting wires, and the mating portion comprises an arcuate edge of the contact. In the latter disposition, the capacitance plate portion would extend rearwardly, away from the mating end of the connector, and positionable above wires of a cable for connection to the plug, such that a compact arrangement is achieved.